| Message ID | 20210726165743.232073-1-ani@anisinha.ca (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v3] hw/acpi: add an assertion check for non-null return from acpi_get_i386_pci_host | expand |
On Mon, Jul 26, 2021 at 10:27:43PM +0530, Ani Sinha wrote: > All existing code using acpi_get_i386_pci_host() checks for a non-null > return value from this function call. Instead of returning early when the value > returned is NULL, assert instead. Since there are only two possible host buses > for i386 - q35 and i440fx, a null value return from the function does not make > sense in most cases and is likely an error situation. add "on i386"? > Fixes: c0e427d6eb5fef ("hw/acpi/ich9: Enable ACPI PCI hot-plug") This that seems inappropriate, this is not a bugfix. > > Signed-off-by: Ani Sinha <ani@anisinha.ca> Frankly I don't see this as a useful cleanup. assert is generally a last resort thing. > --- > hw/acpi/pcihp.c | 8 ++++++++ > hw/i386/acpi-build.c | 15 ++++++--------- > 2 files changed, 14 insertions(+), 9 deletions(-) > > changelog: > v1: initial patch > v2: removed comment addition - that can be sent as a separate patch. > v3: added assertion for null host values for all cases except one. > > diff --git a/hw/acpi/pcihp.c b/hw/acpi/pcihp.c > index f4d706e47d..054ee8cbc5 100644 > --- a/hw/acpi/pcihp.c > +++ b/hw/acpi/pcihp.c > @@ -116,6 +116,12 @@ static void acpi_set_pci_info(void) > bsel_is_set = true; > > if (!host) { > + /* > + * This function can be eventually called from > + * qemu_devices_reset() -> acpi_pcihp_reset() even > + * for architectures other than i386. Hence, we need why call out i386 here? well because currently host is only non-null for q35 and i440fx which are both i386. all the above is not a given and we won't remember to update the comment if we change it. Generally graceful failure is the default or should be. > + * to ignore null values for host here. > + */ > return; > } > > @@ -136,6 +142,8 @@ static void acpi_pcihp_disable_root_bus(void) > return; > } > > + assert(host); > + > bus = PCI_HOST_BRIDGE(host)->bus; > if (bus) { > /* setting the hotplug handler to NULL makes the bus non-hotpluggable */ > diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c > index 17836149fe..83fb1d55c0 100644 > --- a/hw/i386/acpi-build.c > +++ b/hw/i386/acpi-build.c > @@ -321,9 +321,7 @@ static void acpi_get_pci_holes(Range *hole, Range *hole64) > > pci_host = acpi_get_i386_pci_host(); > > - if (!pci_host) { > - return; > - } > + assert(pci_host); > > range_set_bounds1(hole, > object_property_get_uint(pci_host, > @@ -1769,9 +1767,9 @@ build_dsdt(GArray *table_data, BIOSLinker *linker, > > pci_host = acpi_get_i386_pci_host(); > > - if (pci_host) { > - bus = PCI_HOST_BRIDGE(pci_host)->bus; > - } > + assert(pci_host); > + > + bus = PCI_HOST_BRIDGE(pci_host)->bus; > > if (bus) { > Aml *scope = aml_scope("PCI0"); > @@ -2389,9 +2387,8 @@ static bool acpi_get_mcfg(AcpiMcfgInfo *mcfg) > QObject *o; > > pci_host = acpi_get_i386_pci_host(); > - if (!pci_host) { > - return false; > - } > + > + assert(pci_host); > > o = object_property_get_qobject(pci_host, PCIE_HOST_MCFG_BASE, NULL); > if (!o) { > -- > 2.25.1
On Wed, 28 Jul 2021, Michael S. Tsirkin wrote: > On Mon, Jul 26, 2021 at 10:27:43PM +0530, Ani Sinha wrote: > > All existing code using acpi_get_i386_pci_host() checks for a non-null > > return value from this function call. Instead of returning early when the value > > returned is NULL, assert instead. Since there are only two possible host buses > > for i386 - q35 and i440fx, a null value return from the function does not make > > sense in most cases and is likely an error situation. > > add "on i386"? > > > Fixes: c0e427d6eb5fef ("hw/acpi/ich9: Enable ACPI PCI hot-plug") > > This that seems inappropriate, this is not a bugfix. > > > > > Signed-off-by: Ani Sinha <ani@anisinha.ca> > > > Frankly I don't see this as a useful cleanup. > assert is generally a last resort thing. > Igor pushed in the direction of assertion. Otherwise, see my v2. > > --- > > hw/acpi/pcihp.c | 8 ++++++++ > > hw/i386/acpi-build.c | 15 ++++++--------- > > 2 files changed, 14 insertions(+), 9 deletions(-) > > > > changelog: > > v1: initial patch > > v2: removed comment addition - that can be sent as a separate patch. > > v3: added assertion for null host values for all cases except one. > > > > diff --git a/hw/acpi/pcihp.c b/hw/acpi/pcihp.c > > index f4d706e47d..054ee8cbc5 100644 > > --- a/hw/acpi/pcihp.c > > +++ b/hw/acpi/pcihp.c > > @@ -116,6 +116,12 @@ static void acpi_set_pci_info(void) > > bsel_is_set = true; > > > > if (!host) { > > + /* > > + * This function can be eventually called from > > + * qemu_devices_reset() -> acpi_pcihp_reset() even > > + * for architectures other than i386. Hence, we need > > why call out i386 here? well because currently host > is only non-null for q35 and i440fx which are both i386. > all the above is not a given and we won't remember to update > the comment if we change it. Generally graceful failure > is the default or should be. Hmm. there is much debate to be had about graceful and unfraceful failures :-) Some might say ungraceful failures helps to catch issues earlier before the state is messed up.
On Wed, 28 Jul 2021, Michael S. Tsirkin wrote: > On Mon, Jul 26, 2021 at 10:27:43PM +0530, Ani Sinha wrote: > > All existing code using acpi_get_i386_pci_host() checks for a non-null > > return value from this function call. Instead of returning early when the value > > returned is NULL, assert instead. Since there are only two possible host buses > > for i386 - q35 and i440fx, a null value return from the function does not make > > sense in most cases and is likely an error situation. > > add "on i386"? > > > Fixes: c0e427d6eb5fef ("hw/acpi/ich9: Enable ACPI PCI hot-plug") > > This that seems inappropriate, this is not a bugfix. > Forgot to answer this. I started this patch because I saw a gap that was introduced with the above patch. In acpi_pcihp_disable_root_bus(), Julia's code did not check for null return value from acpi_get_i386_pci_host(). See v2. Hence, I added the fixes tag. Then Igor suggested that I assert instead and I also thought perhaps assertion is a better idea. Hence v3. I am not conflicted after reading your argument. We should assert only when a certain invariant is always respected. Otherwise we should not assert. If you think acpi_get_i386_pci_host() can be called from non-i386 path as well, maybe v2 approach is better.
On Thu, 29 Jul 2021, Ani Sinha wrote: > > > On Wed, 28 Jul 2021, Michael S. Tsirkin wrote: > > > On Mon, Jul 26, 2021 at 10:27:43PM +0530, Ani Sinha wrote: > > > All existing code using acpi_get_i386_pci_host() checks for a non-null > > > return value from this function call. Instead of returning early when the value > > > returned is NULL, assert instead. Since there are only two possible host buses > > > for i386 - q35 and i440fx, a null value return from the function does not make > > > sense in most cases and is likely an error situation. > > > > add "on i386"? > > > > > Fixes: c0e427d6eb5fef ("hw/acpi/ich9: Enable ACPI PCI hot-plug") > > > > This that seems inappropriate, this is not a bugfix. > > > > Forgot to answer this. I started this patch because I saw a gap that was > introduced with the above patch. In acpi_pcihp_disable_root_bus(), Julia's > code did not check for null return value from acpi_get_i386_pci_host(). > See v2. Hence, I added the fixes tag. Then Igor suggested that I assert > instead and I also thought perhaps assertion is a better idea. Hence v3. I > am not conflicted after reading your argument. We should assert only when > a certain invariant is always respected. Otherwise we should not assert. > If you think acpi_get_i386_pci_host() can be called from non-i386 path as > well, maybe v2 approach is better. Also I should point out that at this moment, only ich9 and piix4 end up calling acpi_pcihp_disable_root_bus(). Hence, we are ok either way for now. In the future, if other archs end of calling this function, then the question is, do we gracefully fail by simply returning in case of null host bridge or do we assert? In its current form, it will ungracefully crash somewhere.
ping ... On Thu, 29 Jul 2021, Ani Sinha wrote: > > > On Thu, 29 Jul 2021, Ani Sinha wrote: > > > > > > > On Wed, 28 Jul 2021, Michael S. Tsirkin wrote: > > > > > On Mon, Jul 26, 2021 at 10:27:43PM +0530, Ani Sinha wrote: > > > > All existing code using acpi_get_i386_pci_host() checks for a non-null > > > > return value from this function call. Instead of returning early when the value > > > > returned is NULL, assert instead. Since there are only two possible host buses > > > > for i386 - q35 and i440fx, a null value return from the function does not make > > > > sense in most cases and is likely an error situation. > > > > > > add "on i386"? > > > > > > > Fixes: c0e427d6eb5fef ("hw/acpi/ich9: Enable ACPI PCI hot-plug") > > > > > > This that seems inappropriate, this is not a bugfix. > > > > > > > Forgot to answer this. I started this patch because I saw a gap that was > > introduced with the above patch. In acpi_pcihp_disable_root_bus(), Julia's > > code did not check for null return value from acpi_get_i386_pci_host(). > > See v2. Hence, I added the fixes tag. Then Igor suggested that I assert > > instead and I also thought perhaps assertion is a better idea. Hence v3. I > > am not conflicted after reading your argument. We should assert only when > > a certain invariant is always respected. Otherwise we should not assert. > > If you think acpi_get_i386_pci_host() can be called from non-i386 path as > > well, maybe v2 approach is better. > > Also I should point out that at this moment, only ich9 and piix4 end up > calling acpi_pcihp_disable_root_bus(). Hence, we are ok either way for > now. In the future, if other archs end of calling this function, then the > question is, do we gracefully fail by simply returning in case of null > host bridge or do we assert? In its current form, it will ungracefully > crash somewhere. > >
On Mon, 26 Jul 2021 22:27:43 +0530 Ani Sinha <ani@anisinha.ca> wrote: > All existing code using acpi_get_i386_pci_host() checks for a non-null > return value from this function call. Instead of returning early when the value > returned is NULL, assert instead. Since there are only two possible host buses > for i386 - q35 and i440fx, a null value return from the function does not make > sense in most cases and is likely an error situation. > > Fixes: c0e427d6eb5fef ("hw/acpi/ich9: Enable ACPI PCI hot-plug") > > Signed-off-by: Ani Sinha <ani@anisinha.ca> > --- > hw/acpi/pcihp.c | 8 ++++++++ > hw/i386/acpi-build.c | 15 ++++++--------- > 2 files changed, 14 insertions(+), 9 deletions(-) > > changelog: > v1: initial patch > v2: removed comment addition - that can be sent as a separate patch. > v3: added assertion for null host values for all cases except one. > > diff --git a/hw/acpi/pcihp.c b/hw/acpi/pcihp.c > index f4d706e47d..054ee8cbc5 100644 > --- a/hw/acpi/pcihp.c > +++ b/hw/acpi/pcihp.c > @@ -116,6 +116,12 @@ static void acpi_set_pci_info(void) > bsel_is_set = true; > > if (!host) { > + /* > + * This function can be eventually called from > + * qemu_devices_reset() -> acpi_pcihp_reset() even > + * for architectures other than i386. Hence, we need > + * to ignore null values for host here. > + */ > return; > } I suspect it's a MIPS target that call this code unnecessarily. It would be better to get rid of this condition altogether. Frr that I can suggest to make acpi_pcihp_reset() stub and replace pcihp.c with stub (perhaps use acpi-x86-stub.c) when building for MIPS. then a bunch of asserts/ifs won't be necessary, just one in acpi_get_i386_pci_host() will be sufficient. > @@ -136,6 +142,8 @@ static void acpi_pcihp_disable_root_bus(void) > return; > } > > + assert(host); > + > bus = PCI_HOST_BRIDGE(host)->bus; > if (bus) { > /* setting the hotplug handler to NULL makes the bus non-hotpluggable */ > diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c > index 17836149fe..83fb1d55c0 100644 > --- a/hw/i386/acpi-build.c > +++ b/hw/i386/acpi-build.c > @@ -321,9 +321,7 @@ static void acpi_get_pci_holes(Range *hole, Range *hole64) > > pci_host = acpi_get_i386_pci_host(); > > - if (!pci_host) { > - return; > - } > + assert(pci_host); > > range_set_bounds1(hole, > object_property_get_uint(pci_host, > @@ -1769,9 +1767,9 @@ build_dsdt(GArray *table_data, BIOSLinker *linker, > > pci_host = acpi_get_i386_pci_host(); > > - if (pci_host) { > - bus = PCI_HOST_BRIDGE(pci_host)->bus; > - } > + assert(pci_host); > + > + bus = PCI_HOST_BRIDGE(pci_host)->bus; > > if (bus) { > Aml *scope = aml_scope("PCI0"); > @@ -2389,9 +2387,8 @@ static bool acpi_get_mcfg(AcpiMcfgInfo *mcfg) > QObject *o; > > pci_host = acpi_get_i386_pci_host(); > - if (!pci_host) { > - return false; > - } > + > + assert(pci_host); > > o = object_property_get_qobject(pci_host, PCIE_HOST_MCFG_BASE, NULL); > if (!o) {
On Thu, 5 Aug 2021, Igor Mammedov wrote: > On Mon, 26 Jul 2021 22:27:43 +0530 > Ani Sinha <ani@anisinha.ca> wrote: > > > All existing code using acpi_get_i386_pci_host() checks for a non-null > > return value from this function call. Instead of returning early when the value > > returned is NULL, assert instead. Since there are only two possible host buses > > for i386 - q35 and i440fx, a null value return from the function does not make > > sense in most cases and is likely an error situation. > > > > Fixes: c0e427d6eb5fef ("hw/acpi/ich9: Enable ACPI PCI hot-plug") > > > > Signed-off-by: Ani Sinha <ani@anisinha.ca> > > --- > > hw/acpi/pcihp.c | 8 ++++++++ > > hw/i386/acpi-build.c | 15 ++++++--------- > > 2 files changed, 14 insertions(+), 9 deletions(-) > > > > changelog: > > v1: initial patch > > v2: removed comment addition - that can be sent as a separate patch. > > v3: added assertion for null host values for all cases except one. > > > > diff --git a/hw/acpi/pcihp.c b/hw/acpi/pcihp.c > > index f4d706e47d..054ee8cbc5 100644 > > --- a/hw/acpi/pcihp.c > > +++ b/hw/acpi/pcihp.c > > @@ -116,6 +116,12 @@ static void acpi_set_pci_info(void) > > bsel_is_set = true; > > > > if (!host) { > > + /* > > + * This function can be eventually called from > > + * qemu_devices_reset() -> acpi_pcihp_reset() even > > + * for architectures other than i386. Hence, we need > > + * to ignore null values for host here. > > + */ > > return; > > } > > I suspect it's a MIPS target that call this code unnecessarily. > It would be better to get rid of this condition altogether. > Frr that I can suggest to make acpi_pcihp_reset() stub and > replace pcihp.c with stub (perhaps use acpi-x86-stub.c) when building > for MIPS. > > then a bunch of asserts/ifs won't be necessary, > just one in acpi_get_i386_pci_host() will be sufficient. > OK this is a good idea. I can see that mips-softmmu-config-devices.h has CONFIG_ACPI_X86 turned on for mips. This does not seem right. The issue here is: $ grep -R CONFIG_ACPI_X86 * devices/mips-softmmu/common.mak:CONFIG_ACPI_X86=y So after -CONFIG_ACPI_X86=y -CONFIG_PIIX4=y (the second one is needed because after removing first one we get: /usr/bin/ld: libcommon.fa.p/hw_isa_piix4.c.o: in function `piix4_create': /home/anisinha/workspace/qemu/build/../hw/isa/piix4.c:269: undefined reference to `piix4_pm_init' This is because in hw/acpi/meson.build, piix4.c is conditional on CONFIG_ACPI_X86. ) /usr/bin/ld: libqemu-mips-softmmu.fa.p/hw_mips_gt64xxx_pci.c.o: in function `gt64120_pci_set_irq': /home/anisinha/workspace/qemu/build/../hw/mips/gt64xxx_pci.c:1020: undefined reference to `piix4_dev' /usr/bin/ld: libqemu-mips-softmmu.fa.p/hw_mips_malta.c.o: in function `mips_malta_init': /home/anisinha/workspace/qemu/build/../hw/mips/malta.c:1404: undefined reference to `piix4_create' So should mips be doing piix stuff anyway? Is Piix4 etc not x86 specific? How to handle this?
On Thu, 5 Aug 2021, Ani Sinha wrote: > > > On Thu, 5 Aug 2021, Igor Mammedov wrote: > > > On Mon, 26 Jul 2021 22:27:43 +0530 > > Ani Sinha <ani@anisinha.ca> wrote: > > > > > All existing code using acpi_get_i386_pci_host() checks for a non-null > > > return value from this function call. Instead of returning early when the value > > > returned is NULL, assert instead. Since there are only two possible host buses > > > for i386 - q35 and i440fx, a null value return from the function does not make > > > sense in most cases and is likely an error situation. > > > > > > Fixes: c0e427d6eb5fef ("hw/acpi/ich9: Enable ACPI PCI hot-plug") > > > > > > Signed-off-by: Ani Sinha <ani@anisinha.ca> > > > --- > > > hw/acpi/pcihp.c | 8 ++++++++ > > > hw/i386/acpi-build.c | 15 ++++++--------- > > > 2 files changed, 14 insertions(+), 9 deletions(-) > > > > > > changelog: > > > v1: initial patch > > > v2: removed comment addition - that can be sent as a separate patch. > > > v3: added assertion for null host values for all cases except one. > > > > > > diff --git a/hw/acpi/pcihp.c b/hw/acpi/pcihp.c > > > index f4d706e47d..054ee8cbc5 100644 > > > --- a/hw/acpi/pcihp.c > > > +++ b/hw/acpi/pcihp.c > > > @@ -116,6 +116,12 @@ static void acpi_set_pci_info(void) > > > bsel_is_set = true; > > > > > > if (!host) { > > > + /* > > > + * This function can be eventually called from > > > + * qemu_devices_reset() -> acpi_pcihp_reset() even > > > + * for architectures other than i386. Hence, we need > > > + * to ignore null values for host here. > > > + */ > > > return; > > > } > > > > I suspect it's a MIPS target that call this code unnecessarily. > > It would be better to get rid of this condition altogether. > > Frr that I can suggest to make acpi_pcihp_reset() stub and > > replace pcihp.c with stub (perhaps use acpi-x86-stub.c) when building > > for MIPS. > > > > then a bunch of asserts/ifs won't be necessary, > > just one in acpi_get_i386_pci_host() will be sufficient. > > > > OK this is a good idea. > I can see that mips-softmmu-config-devices.h has > CONFIG_ACPI_X86 turned on for mips. This does not seem right. > > The issue here is: > > $ grep -R CONFIG_ACPI_X86 * > devices/mips-softmmu/common.mak:CONFIG_ACPI_X86=y > > So after > > -CONFIG_ACPI_X86=y > -CONFIG_PIIX4=y > > (the second one is needed because after removing first one we get: > > /usr/bin/ld: libcommon.fa.p/hw_isa_piix4.c.o: in function `piix4_create': > /home/anisinha/workspace/qemu/build/../hw/isa/piix4.c:269: undefined > reference to `piix4_pm_init' > > This is because in hw/acpi/meson.build, piix4.c is conditional on > CONFIG_ACPI_X86. ) > > /usr/bin/ld: libqemu-mips-softmmu.fa.p/hw_mips_gt64xxx_pci.c.o: in > function `gt64120_pci_set_irq': > /home/anisinha/workspace/qemu/build/../hw/mips/gt64xxx_pci.c:1020: > undefined reference to `piix4_dev' > /usr/bin/ld: libqemu-mips-softmmu.fa.p/hw_mips_malta.c.o: in function > `mips_malta_init': > /home/anisinha/workspace/qemu/build/../hw/mips/malta.c:1404: undefined > reference to `piix4_create' > > So should mips be doing piix stuff anyway? Is Piix4 etc not x86 specific? Apparently this is by design: https://qemu.readthedocs.io/en/stable/system/target-mips.html which means mips malta will continue to use the x86 specific functions like acpi_pcihp_reset(). Creating a stub for this with acpi-x86-stub.c will result in a double symbol definition because CONFIG_PC is off for mips.
On Thu, 5 Aug 2021, Ani Sinha wrote: > > > On Thu, 5 Aug 2021, Ani Sinha wrote: > > > > > > > On Thu, 5 Aug 2021, Igor Mammedov wrote: > > > > > On Mon, 26 Jul 2021 22:27:43 +0530 > > > Ani Sinha <ani@anisinha.ca> wrote: > > > > > > > All existing code using acpi_get_i386_pci_host() checks for a non-null > > > > return value from this function call. Instead of returning early when the value > > > > returned is NULL, assert instead. Since there are only two possible host buses > > > > for i386 - q35 and i440fx, a null value return from the function does not make > > > > sense in most cases and is likely an error situation. > > > > > > > > Fixes: c0e427d6eb5fef ("hw/acpi/ich9: Enable ACPI PCI hot-plug") > > > > > > > > Signed-off-by: Ani Sinha <ani@anisinha.ca> > > > > --- > > > > hw/acpi/pcihp.c | 8 ++++++++ > > > > hw/i386/acpi-build.c | 15 ++++++--------- > > > > 2 files changed, 14 insertions(+), 9 deletions(-) > > > > > > > > changelog: > > > > v1: initial patch > > > > v2: removed comment addition - that can be sent as a separate patch. > > > > v3: added assertion for null host values for all cases except one. > > > > > > > > diff --git a/hw/acpi/pcihp.c b/hw/acpi/pcihp.c > > > > index f4d706e47d..054ee8cbc5 100644 > > > > --- a/hw/acpi/pcihp.c > > > > +++ b/hw/acpi/pcihp.c > > > > @@ -116,6 +116,12 @@ static void acpi_set_pci_info(void) > > > > bsel_is_set = true; > > > > > > > > if (!host) { > > > > + /* > > > > + * This function can be eventually called from > > > > + * qemu_devices_reset() -> acpi_pcihp_reset() even > > > > + * for architectures other than i386. Hence, we need > > > > + * to ignore null values for host here. > > > > + */ > > > > return; > > > > } > > > > > > I suspect it's a MIPS target that call this code unnecessarily. > > > It would be better to get rid of this condition altogether. > > > Frr that I can suggest to make acpi_pcihp_reset() stub and > > > replace pcihp.c with stub (perhaps use acpi-x86-stub.c) when building > > > for MIPS. > > > > > > then a bunch of asserts/ifs won't be necessary, > > > just one in acpi_get_i386_pci_host() will be sufficient. > > > > > > > OK this is a good idea. > > I can see that mips-softmmu-config-devices.h has > > CONFIG_ACPI_X86 turned on for mips. This does not seem right. > > > > The issue here is: > > > > $ grep -R CONFIG_ACPI_X86 * > > devices/mips-softmmu/common.mak:CONFIG_ACPI_X86=y > > > > So after > > > > -CONFIG_ACPI_X86=y > > -CONFIG_PIIX4=y > > > > (the second one is needed because after removing first one we get: > > > > /usr/bin/ld: libcommon.fa.p/hw_isa_piix4.c.o: in function `piix4_create': > > /home/anisinha/workspace/qemu/build/../hw/isa/piix4.c:269: undefined > > reference to `piix4_pm_init' > > > > This is because in hw/acpi/meson.build, piix4.c is conditional on > > CONFIG_ACPI_X86. ) > > > > /usr/bin/ld: libqemu-mips-softmmu.fa.p/hw_mips_gt64xxx_pci.c.o: in > > function `gt64120_pci_set_irq': > > /home/anisinha/workspace/qemu/build/../hw/mips/gt64xxx_pci.c:1020: > > undefined reference to `piix4_dev' > > /usr/bin/ld: libqemu-mips-softmmu.fa.p/hw_mips_malta.c.o: in function > > `mips_malta_init': > > /home/anisinha/workspace/qemu/build/../hw/mips/malta.c:1404: undefined > > reference to `piix4_create' > > > > So should mips be doing piix stuff anyway? Is Piix4 etc not x86 specific? > > Apparently this is by design: > https://qemu.readthedocs.io/en/stable/system/target-mips.html > > which means mips malta will continue to use the x86 specific functions > like acpi_pcihp_reset(). Creating a stub for this with acpi-x86-stub.c > will result in a double symbol definition because CONFIG_PC is off for > mips. > Also to be noted that there is a stub for acpi_get_i386_pci_host() which simply returns NULL. This activates when CONFIG_PC is disabled. It is this stub that gets called for mips and hence the check for non-null host is needed in acpi_set_pci_info() function.
On Thu, Aug 05, 2021 at 07:42:35PM +0530, Ani Sinha wrote: > Also to be noted that there is a stub for acpi_get_i386_pci_host() which > simply returns NULL. This activates when CONFIG_PC is disabled. It is this > stub that gets called for mips and hence the check for non-null host is > needed in acpi_set_pci_info() function. > Frankly this is generating more discussion that it's worth imho. IMHO these tweaks will bring little benefit. Igor do you feel differently?
On Thu, 5 Aug 2021 18:13:21 -0400 "Michael S. Tsirkin" <mst@redhat.com> wrote: > On Thu, Aug 05, 2021 at 07:42:35PM +0530, Ani Sinha wrote: > > Also to be noted that there is a stub for acpi_get_i386_pci_host() which > > simply returns NULL. This activates when CONFIG_PC is disabled. It is this > > stub that gets called for mips and hence the check for non-null host is > > needed in acpi_set_pci_info() function. > > > > Frankly this is generating more discussion that it's worth imho. > IMHO these tweaks will bring little benefit. > Igor do you feel differently? replacing 'ifs' with assert is a bit cleaner, but if we are cleaning it up we should clean up it properly without leaving unnecessary code around. That's why I suggested to separate x86 specific parts from piix4. Philippe (CCed) even have reported issues ACPI parts were causing on MIPS machines, so if someone is willing to untangle the mess it might be worth the shot.
On Thu, 5 Aug 2021 19:42:35 +0530 (IST) Ani Sinha <ani@anisinha.ca> wrote: > On Thu, 5 Aug 2021, Ani Sinha wrote: > > > > > > > On Thu, 5 Aug 2021, Ani Sinha wrote: > > > > > > > > > > > On Thu, 5 Aug 2021, Igor Mammedov wrote: > > > > > > > On Mon, 26 Jul 2021 22:27:43 +0530 > > > > Ani Sinha <ani@anisinha.ca> wrote: > > > > > > > > > All existing code using acpi_get_i386_pci_host() checks for a non-null > > > > > return value from this function call. Instead of returning early when the value > > > > > returned is NULL, assert instead. Since there are only two possible host buses > > > > > for i386 - q35 and i440fx, a null value return from the function does not make > > > > > sense in most cases and is likely an error situation. > > > > > > > > > > Fixes: c0e427d6eb5fef ("hw/acpi/ich9: Enable ACPI PCI hot-plug") > > > > > > > > > > Signed-off-by: Ani Sinha <ani@anisinha.ca> > > > > > --- > > > > > hw/acpi/pcihp.c | 8 ++++++++ > > > > > hw/i386/acpi-build.c | 15 ++++++--------- > > > > > 2 files changed, 14 insertions(+), 9 deletions(-) > > > > > > > > > > changelog: > > > > > v1: initial patch > > > > > v2: removed comment addition - that can be sent as a separate patch. > > > > > v3: added assertion for null host values for all cases except one. > > > > > > > > > > diff --git a/hw/acpi/pcihp.c b/hw/acpi/pcihp.c > > > > > index f4d706e47d..054ee8cbc5 100644 > > > > > --- a/hw/acpi/pcihp.c > > > > > +++ b/hw/acpi/pcihp.c > > > > > @@ -116,6 +116,12 @@ static void acpi_set_pci_info(void) > > > > > bsel_is_set = true; > > > > > > > > > > if (!host) { > > > > > + /* > > > > > + * This function can be eventually called from > > > > > + * qemu_devices_reset() -> acpi_pcihp_reset() even > > > > > + * for architectures other than i386. Hence, we need > > > > > + * to ignore null values for host here. > > > > > + */ > > > > > return; > > > > > } > > > > > > > > I suspect it's a MIPS target that call this code unnecessarily. > > > > It would be better to get rid of this condition altogether. > > > > Frr that I can suggest to make acpi_pcihp_reset() stub and > > > > replace pcihp.c with stub (perhaps use acpi-x86-stub.c) when building > > > > for MIPS. > > > > > > > > then a bunch of asserts/ifs won't be necessary, > > > > just one in acpi_get_i386_pci_host() will be sufficient. > > > > > > > > > > OK this is a good idea. > > > I can see that mips-softmmu-config-devices.h has > > > CONFIG_ACPI_X86 turned on for mips. This does not seem right. > > > > > > The issue here is: > > > > > > $ grep -R CONFIG_ACPI_X86 * > > > devices/mips-softmmu/common.mak:CONFIG_ACPI_X86=y > > > > > > So after > > > > > > -CONFIG_ACPI_X86=y > > > -CONFIG_PIIX4=y > > > > > > (the second one is needed because after removing first one we get: > > > > > > /usr/bin/ld: libcommon.fa.p/hw_isa_piix4.c.o: in function `piix4_create': > > > /home/anisinha/workspace/qemu/build/../hw/isa/piix4.c:269: undefined > > > reference to `piix4_pm_init' > > > > > > This is because in hw/acpi/meson.build, piix4.c is conditional on > > > CONFIG_ACPI_X86. ) > > > > > > /usr/bin/ld: libqemu-mips-softmmu.fa.p/hw_mips_gt64xxx_pci.c.o: in > > > function `gt64120_pci_set_irq': > > > /home/anisinha/workspace/qemu/build/../hw/mips/gt64xxx_pci.c:1020: > > > undefined reference to `piix4_dev' > > > /usr/bin/ld: libqemu-mips-softmmu.fa.p/hw_mips_malta.c.o: in function > > > `mips_malta_init': > > > /home/anisinha/workspace/qemu/build/../hw/mips/malta.c:1404: undefined > > > reference to `piix4_create' > > > > > > So should mips be doing piix stuff anyway? Is Piix4 etc not x86 specific? > > > > Apparently this is by design: > > https://qemu.readthedocs.io/en/stable/system/target-mips.html > > > > which means mips malta will continue to use the x86 specific functions > > like acpi_pcihp_reset(). Creating a stub for this with acpi-x86-stub.c > > will result in a double symbol definition because CONFIG_PC is off for > > mips. > > > > Also to be noted that there is a stub for acpi_get_i386_pci_host() which > simply returns NULL. This activates when CONFIG_PC is disabled. It is this > stub that gets called for mips and hence the check for non-null host is > needed in acpi_set_pci_info() function. that were half measures to deal around code that shouldn't be called, now with pcihp being used by both pc and q35 we don't have reason to keep around null checks modulo mips calling code that shouldn't be called there to begin with.
On Fri, 6 Aug 2021, Igor Mammedov wrote: > On Thu, 5 Aug 2021 19:42:35 +0530 (IST) > Ani Sinha <ani@anisinha.ca> wrote: > > > On Thu, 5 Aug 2021, Ani Sinha wrote: > > > > > > > > > > > On Thu, 5 Aug 2021, Ani Sinha wrote: > > > > > > > > > > > > > > > On Thu, 5 Aug 2021, Igor Mammedov wrote: > > > > > > > > > On Mon, 26 Jul 2021 22:27:43 +0530 > > > > > Ani Sinha <ani@anisinha.ca> wrote: > > > > > > > > > > > All existing code using acpi_get_i386_pci_host() checks for a non-null > > > > > > return value from this function call. Instead of returning early when the value > > > > > > returned is NULL, assert instead. Since there are only two possible host buses > > > > > > for i386 - q35 and i440fx, a null value return from the function does not make > > > > > > sense in most cases and is likely an error situation. > > > > > > > > > > > > Fixes: c0e427d6eb5fef ("hw/acpi/ich9: Enable ACPI PCI hot-plug") > > > > > > > > > > > > Signed-off-by: Ani Sinha <ani@anisinha.ca> > > > > > > --- > > > > > > hw/acpi/pcihp.c | 8 ++++++++ > > > > > > hw/i386/acpi-build.c | 15 ++++++--------- > > > > > > 2 files changed, 14 insertions(+), 9 deletions(-) > > > > > > > > > > > > changelog: > > > > > > v1: initial patch > > > > > > v2: removed comment addition - that can be sent as a separate patch. > > > > > > v3: added assertion for null host values for all cases except one. > > > > > > > > > > > > diff --git a/hw/acpi/pcihp.c b/hw/acpi/pcihp.c > > > > > > index f4d706e47d..054ee8cbc5 100644 > > > > > > --- a/hw/acpi/pcihp.c > > > > > > +++ b/hw/acpi/pcihp.c > > > > > > @@ -116,6 +116,12 @@ static void acpi_set_pci_info(void) > > > > > > bsel_is_set = true; > > > > > > > > > > > > if (!host) { > > > > > > + /* > > > > > > + * This function can be eventually called from > > > > > > + * qemu_devices_reset() -> acpi_pcihp_reset() even > > > > > > + * for architectures other than i386. Hence, we need > > > > > > + * to ignore null values for host here. > > > > > > + */ > > > > > > return; > > > > > > } > > > > > > > > > > I suspect it's a MIPS target that call this code unnecessarily. > > > > > It would be better to get rid of this condition altogether. > > > > > Frr that I can suggest to make acpi_pcihp_reset() stub and > > > > > replace pcihp.c with stub (perhaps use acpi-x86-stub.c) when building > > > > > for MIPS. > > > > > > > > > > then a bunch of asserts/ifs won't be necessary, > > > > > just one in acpi_get_i386_pci_host() will be sufficient. > > > > > > > > > > > > > OK this is a good idea. > > > > I can see that mips-softmmu-config-devices.h has > > > > CONFIG_ACPI_X86 turned on for mips. This does not seem right. > > > > > > > > The issue here is: > > > > > > > > $ grep -R CONFIG_ACPI_X86 * > > > > devices/mips-softmmu/common.mak:CONFIG_ACPI_X86=y > > > > > > > > So after > > > > > > > > -CONFIG_ACPI_X86=y > > > > -CONFIG_PIIX4=y > > > > > > > > (the second one is needed because after removing first one we get: > > > > > > > > /usr/bin/ld: libcommon.fa.p/hw_isa_piix4.c.o: in function `piix4_create': > > > > /home/anisinha/workspace/qemu/build/../hw/isa/piix4.c:269: undefined > > > > reference to `piix4_pm_init' > > > > > > > > This is because in hw/acpi/meson.build, piix4.c is conditional on > > > > CONFIG_ACPI_X86. ) > > > > > > > > /usr/bin/ld: libqemu-mips-softmmu.fa.p/hw_mips_gt64xxx_pci.c.o: in > > > > function `gt64120_pci_set_irq': > > > > /home/anisinha/workspace/qemu/build/../hw/mips/gt64xxx_pci.c:1020: > > > > undefined reference to `piix4_dev' > > > > /usr/bin/ld: libqemu-mips-softmmu.fa.p/hw_mips_malta.c.o: in function > > > > `mips_malta_init': > > > > /home/anisinha/workspace/qemu/build/../hw/mips/malta.c:1404: undefined > > > > reference to `piix4_create' > > > > > > > > So should mips be doing piix stuff anyway? Is Piix4 etc not x86 specific? > > > > > > Apparently this is by design: > > > https://qemu.readthedocs.io/en/stable/system/target-mips.html > > > > > > which means mips malta will continue to use the x86 specific functions > > > like acpi_pcihp_reset(). Creating a stub for this with acpi-x86-stub.c > > > will result in a double symbol definition because CONFIG_PC is off for > > > mips. > > > > > > > Also to be noted that there is a stub for acpi_get_i386_pci_host() which > > simply returns NULL. This activates when CONFIG_PC is disabled. It is this > > stub that gets called for mips and hence the check for non-null host is > > needed in acpi_set_pci_info() function. > that were half measures to deal around code that shouldn't be called, > now with pcihp being used by both pc and q35 we don't have reason to > keep around null checks modulo mips calling code that shouldn't be > called there to begin with. So malta mips does not need ACPI hotplug? In that case, maybe we should not make pcihp.c dependent on CONFIG_ACPI_X86. Ideas welcome.
On 8/6/21 12:52 PM, Ani Sinha wrote: > On Fri, 6 Aug 2021, Igor Mammedov wrote: >> On Thu, 5 Aug 2021 19:42:35 +0530 (IST) >> Ani Sinha <ani@anisinha.ca> wrote: >>> On Thu, 5 Aug 2021, Ani Sinha wrote: >>>> On Thu, 5 Aug 2021, Ani Sinha wrote: >>>>> On Thu, 5 Aug 2021, Igor Mammedov wrote: >>>>>> On Mon, 26 Jul 2021 22:27:43 +0530 >>>>>> Ani Sinha <ani@anisinha.ca> wrote: >>>>>> >>>>>>> All existing code using acpi_get_i386_pci_host() checks for a non-null >>>>>>> return value from this function call. Instead of returning early when the value >>>>>>> returned is NULL, assert instead. Since there are only two possible host buses >>>>>>> for i386 - q35 and i440fx, a null value return from the function does not make >>>>>>> sense in most cases and is likely an error situation. >>>>>>> >>>>>>> Fixes: c0e427d6eb5fef ("hw/acpi/ich9: Enable ACPI PCI hot-plug") >>>>>>> >>>>>>> Signed-off-by: Ani Sinha <ani@anisinha.ca> >>>>>>> --- >>>>>>> hw/acpi/pcihp.c | 8 ++++++++ >>>>>>> hw/i386/acpi-build.c | 15 ++++++--------- >>>>>>> 2 files changed, 14 insertions(+), 9 deletions(-) >>>>>>> >>>>>>> changelog: >>>>>>> v1: initial patch >>>>>>> v2: removed comment addition - that can be sent as a separate patch. >>>>>>> v3: added assertion for null host values for all cases except one. >>>>>>> >>>>>>> diff --git a/hw/acpi/pcihp.c b/hw/acpi/pcihp.c >>>>>>> index f4d706e47d..054ee8cbc5 100644 >>>>>>> --- a/hw/acpi/pcihp.c >>>>>>> +++ b/hw/acpi/pcihp.c >>>>>>> @@ -116,6 +116,12 @@ static void acpi_set_pci_info(void) >>>>>>> bsel_is_set = true; >>>>>>> >>>>>>> if (!host) { >>>>>>> + /* >>>>>>> + * This function can be eventually called from >>>>>>> + * qemu_devices_reset() -> acpi_pcihp_reset() even >>>>>>> + * for architectures other than i386. Hence, we need >>>>>>> + * to ignore null values for host here. >>>>>>> + */ >>>>>>> return; >>>>>>> } >>>>>> >>>>>> I suspect it's a MIPS target that call this code unnecessarily. >>>>>> It would be better to get rid of this condition altogether. >>>>>> Frr that I can suggest to make acpi_pcihp_reset() stub and >>>>>> replace pcihp.c with stub (perhaps use acpi-x86-stub.c) when building >>>>>> for MIPS. >>>>>> >>>>>> then a bunch of asserts/ifs won't be necessary, >>>>>> just one in acpi_get_i386_pci_host() will be sufficient. >>>>>> >>>>> >>>>> OK this is a good idea. >>>>> I can see that mips-softmmu-config-devices.h has >>>>> CONFIG_ACPI_X86 turned on for mips. This does not seem right. >>>>> >>>>> The issue here is: >>>>> >>>>> $ grep -R CONFIG_ACPI_X86 * >>>>> devices/mips-softmmu/common.mak:CONFIG_ACPI_X86=y >>>>> >>>>> So after >>>>> >>>>> -CONFIG_ACPI_X86=y >>>>> -CONFIG_PIIX4=y >>>>> >>>>> (the second one is needed because after removing first one we get: >>>>> >>>>> /usr/bin/ld: libcommon.fa.p/hw_isa_piix4.c.o: in function `piix4_create': >>>>> /home/anisinha/workspace/qemu/build/../hw/isa/piix4.c:269: undefined >>>>> reference to `piix4_pm_init' >>>>> >>>>> This is because in hw/acpi/meson.build, piix4.c is conditional on >>>>> CONFIG_ACPI_X86. ) >>>>> >>>>> /usr/bin/ld: libqemu-mips-softmmu.fa.p/hw_mips_gt64xxx_pci.c.o: in >>>>> function `gt64120_pci_set_irq': >>>>> /home/anisinha/workspace/qemu/build/../hw/mips/gt64xxx_pci.c:1020: >>>>> undefined reference to `piix4_dev' >>>>> /usr/bin/ld: libqemu-mips-softmmu.fa.p/hw_mips_malta.c.o: in function >>>>> `mips_malta_init': >>>>> /home/anisinha/workspace/qemu/build/../hw/mips/malta.c:1404: undefined >>>>> reference to `piix4_create' >>>>> >>>>> So should mips be doing piix stuff anyway? Is Piix4 etc not x86 specific? PIIX, PIIX3 and PIIX4 are generic chipsets, not X86-specific. QEMU's PIIX3 is a Frankenstein to support virtualization to a chipset not designed for it. If you look at it, the X86 machine use a PIIX3 but the PIIX3 doesn't even provide an ACPI function. It appeared in the PIIX4. The kludge is to instanciate the PIIX4.acpi from the PIIX3 and X86 ppl are happy with it, but it makes it ugly for the other architectures. >>>> Apparently this is by design: >>>> https://qemu.readthedocs.io/en/stable/system/target-mips.html What do you mean "by design"? The Malta uses a PIIX4 chipset for its southbridge indeed. >>>> which means mips malta will continue to use the x86 specific functions >>>> like acpi_pcihp_reset(). Creating a stub for this with acpi-x86-stub.c >>>> will result in a double symbol definition because CONFIG_PC is off for >>>> mips. >>>> >>> >>> Also to be noted that there is a stub for acpi_get_i386_pci_host() which >>> simply returns NULL. This activates when CONFIG_PC is disabled. It is this >>> stub that gets called for mips and hence the check for non-null host is >>> needed in acpi_set_pci_info() function. >> that were half measures to deal around code that shouldn't be called, >> now with pcihp being used by both pc and q35 we don't have reason to >> keep around null checks modulo mips calling code that shouldn't be >> called there to begin with. > > So malta mips does not need ACPI hotplug? In that case, maybe we should > not make pcihp.c dependent on CONFIG_ACPI_X86. Ideas welcome. Linux on Malta does use the ACPI features from the PIIX4. Please dig in the archives, Igor / myself already argued enough about this topic 2 years ago. The consensus was "yes, it is badly implemented, but it works and we don't have time to get it cleaner, pc machine is way more used than the malta one, so let not break the pc machines." See: https://www.mail-archive.com/qemu-devel@nongnu.org/msg613194.html https://www.mail-archive.com/qemu-devel@nongnu.org/msg690435.html https://www.mail-archive.com/qemu-devel@nongnu.org/msg725504.html
On 8/6/21 4:01 PM, Philippe Mathieu-Daudé wrote: > On 8/6/21 12:52 PM, Ani Sinha wrote: >> On Fri, 6 Aug 2021, Igor Mammedov wrote: >>> On Thu, 5 Aug 2021 19:42:35 +0530 (IST) >>> Ani Sinha <ani@anisinha.ca> wrote: >>>> On Thu, 5 Aug 2021, Ani Sinha wrote: >>>>> On Thu, 5 Aug 2021, Ani Sinha wrote: >>>>>> On Thu, 5 Aug 2021, Igor Mammedov wrote: >>>>>>> On Mon, 26 Jul 2021 22:27:43 +0530 >>>>>>> Ani Sinha <ani@anisinha.ca> wrote: >>>>>>> >>>>>>>> All existing code using acpi_get_i386_pci_host() checks for a non-null >>>>>>>> return value from this function call. Instead of returning early when the value >>>>>>>> returned is NULL, assert instead. Since there are only two possible host buses >>>>>>>> for i386 - q35 and i440fx, a null value return from the function does not make >>>>>>>> sense in most cases and is likely an error situation. >>>>>>>> >>>>>>>> Fixes: c0e427d6eb5fef ("hw/acpi/ich9: Enable ACPI PCI hot-plug") >>>>>>>> >>>>>>>> Signed-off-by: Ani Sinha <ani@anisinha.ca> >>>>>>>> --- >>>>>>>> hw/acpi/pcihp.c | 8 ++++++++ >>>>>>>> hw/i386/acpi-build.c | 15 ++++++--------- >>>>>>>> 2 files changed, 14 insertions(+), 9 deletions(-) >>>>>>>> >>>>>>>> changelog: >>>>>>>> v1: initial patch >>>>>>>> v2: removed comment addition - that can be sent as a separate patch. >>>>>>>> v3: added assertion for null host values for all cases except one. >>>>>>>> >>>>>>>> diff --git a/hw/acpi/pcihp.c b/hw/acpi/pcihp.c >>>>>>>> index f4d706e47d..054ee8cbc5 100644 >>>>>>>> --- a/hw/acpi/pcihp.c >>>>>>>> +++ b/hw/acpi/pcihp.c >>>>>>>> @@ -116,6 +116,12 @@ static void acpi_set_pci_info(void) >>>>>>>> bsel_is_set = true; >>>>>>>> >>>>>>>> if (!host) { >>>>>>>> + /* >>>>>>>> + * This function can be eventually called from >>>>>>>> + * qemu_devices_reset() -> acpi_pcihp_reset() even >>>>>>>> + * for architectures other than i386. Hence, we need >>>>>>>> + * to ignore null values for host here. >>>>>>>> + */ >>>>>>>> return; >>>>>>>> } >>>>>>> >>>>>>> I suspect it's a MIPS target that call this code unnecessarily. >>>>>>> It would be better to get rid of this condition altogether. >>>>>>> Frr that I can suggest to make acpi_pcihp_reset() stub and >>>>>>> replace pcihp.c with stub (perhaps use acpi-x86-stub.c) when building >>>>>>> for MIPS. >>>>>>> >>>>>>> then a bunch of asserts/ifs won't be necessary, >>>>>>> just one in acpi_get_i386_pci_host() will be sufficient. >>>>>>> >>>>>> >>>>>> OK this is a good idea. >>>>>> I can see that mips-softmmu-config-devices.h has >>>>>> CONFIG_ACPI_X86 turned on for mips. This does not seem right. >>>>>> >>>>>> The issue here is: >>>>>> >>>>>> $ grep -R CONFIG_ACPI_X86 * >>>>>> devices/mips-softmmu/common.mak:CONFIG_ACPI_X86=y >>>>>> >>>>>> So after >>>>>> >>>>>> -CONFIG_ACPI_X86=y >>>>>> -CONFIG_PIIX4=y >>>>>> >>>>>> (the second one is needed because after removing first one we get: >>>>>> >>>>>> /usr/bin/ld: libcommon.fa.p/hw_isa_piix4.c.o: in function `piix4_create': >>>>>> /home/anisinha/workspace/qemu/build/../hw/isa/piix4.c:269: undefined >>>>>> reference to `piix4_pm_init' >>>>>> >>>>>> This is because in hw/acpi/meson.build, piix4.c is conditional on >>>>>> CONFIG_ACPI_X86. ) >>>>>> >>>>>> /usr/bin/ld: libqemu-mips-softmmu.fa.p/hw_mips_gt64xxx_pci.c.o: in >>>>>> function `gt64120_pci_set_irq': >>>>>> /home/anisinha/workspace/qemu/build/../hw/mips/gt64xxx_pci.c:1020: >>>>>> undefined reference to `piix4_dev' >>>>>> /usr/bin/ld: libqemu-mips-softmmu.fa.p/hw_mips_malta.c.o: in function >>>>>> `mips_malta_init': >>>>>> /home/anisinha/workspace/qemu/build/../hw/mips/malta.c:1404: undefined >>>>>> reference to `piix4_create' >>>>>> >>>>>> So should mips be doing piix stuff anyway? Is Piix4 etc not x86 specific? > > PIIX, PIIX3 and PIIX4 are generic chipsets, not X86-specific. > > QEMU's PIIX3 is a Frankenstein to support virtualization to a chipset > not designed for it. > If you look at it, the X86 machine use a PIIX3 but the PIIX3 doesn't > even provide an ACPI function. It appeared in the PIIX4. The kludge is > to instanciate the PIIX4.acpi from the PIIX3 and X86 ppl are happy with > it, but it makes it ugly for the other architectures. > >>>>> Apparently this is by design: >>>>> https://qemu.readthedocs.io/en/stable/system/target-mips.html > > What do you mean "by design"? The Malta uses a PIIX4 chipset for its > southbridge indeed. > >>>>> which means mips malta will continue to use the x86 specific functions >>>>> like acpi_pcihp_reset(). Creating a stub for this with acpi-x86-stub.c >>>>> will result in a double symbol definition because CONFIG_PC is off for >>>>> mips. >>>>> >>>> >>>> Also to be noted that there is a stub for acpi_get_i386_pci_host() which >>>> simply returns NULL. This activates when CONFIG_PC is disabled. It is this >>>> stub that gets called for mips and hence the check for non-null host is >>>> needed in acpi_set_pci_info() function. >>> that were half measures to deal around code that shouldn't be called, >>> now with pcihp being used by both pc and q35 we don't have reason to >>> keep around null checks modulo mips calling code that shouldn't be >>> called there to begin with. >> >> So malta mips does not need ACPI hotplug? In that case, maybe we should >> not make pcihp.c dependent on CONFIG_ACPI_X86. Ideas welcome. > > Linux on Malta does use the ACPI features from the PIIX4. > > Please dig in the archives, Igor / myself already argued enough about > this topic 2 years ago. The consensus was "yes, it is badly implemented, > but it works and we don't have time to get it cleaner, pc machine is > way more used than the malta one, so let not break the pc machines." > > See: > https://www.mail-archive.com/qemu-devel@nongnu.org/msg613194.html > https://www.mail-archive.com/qemu-devel@nongnu.org/msg690435.html > https://www.mail-archive.com/qemu-devel@nongnu.org/msg725504.html Also: https://gitlab.com/qemu-project/qemu/-/issues/193 https://gitlab.com/qemu-project/qemu/-/issues/221
On Fri, 6 Aug 2021, Philippe Mathieu-Daudé wrote: > On 8/6/21 4:01 PM, Philippe Mathieu-Daudé wrote: > > On 8/6/21 12:52 PM, Ani Sinha wrote: > >> On Fri, 6 Aug 2021, Igor Mammedov wrote: > >>> On Thu, 5 Aug 2021 19:42:35 +0530 (IST) > >>> Ani Sinha <ani@anisinha.ca> wrote: > >>>> On Thu, 5 Aug 2021, Ani Sinha wrote: > >>>>> On Thu, 5 Aug 2021, Ani Sinha wrote: > >>>>>> On Thu, 5 Aug 2021, Igor Mammedov wrote: > >>>>>>> On Mon, 26 Jul 2021 22:27:43 +0530 > >>>>>>> Ani Sinha <ani@anisinha.ca> wrote: > >>>>>>> > >>>>>>>> All existing code using acpi_get_i386_pci_host() checks for a non-null > >>>>>>>> return value from this function call. Instead of returning early when the value > >>>>>>>> returned is NULL, assert instead. Since there are only two possible host buses > >>>>>>>> for i386 - q35 and i440fx, a null value return from the function does not make > >>>>>>>> sense in most cases and is likely an error situation. > >>>>>>>> > >>>>>>>> Fixes: c0e427d6eb5fef ("hw/acpi/ich9: Enable ACPI PCI hot-plug") > >>>>>>>> > >>>>>>>> Signed-off-by: Ani Sinha <ani@anisinha.ca> > >>>>>>>> --- > >>>>>>>> hw/acpi/pcihp.c | 8 ++++++++ > >>>>>>>> hw/i386/acpi-build.c | 15 ++++++--------- > >>>>>>>> 2 files changed, 14 insertions(+), 9 deletions(-) > >>>>>>>> > >>>>>>>> changelog: > >>>>>>>> v1: initial patch > >>>>>>>> v2: removed comment addition - that can be sent as a separate patch. > >>>>>>>> v3: added assertion for null host values for all cases except one. > >>>>>>>> > >>>>>>>> diff --git a/hw/acpi/pcihp.c b/hw/acpi/pcihp.c > >>>>>>>> index f4d706e47d..054ee8cbc5 100644 > >>>>>>>> --- a/hw/acpi/pcihp.c > >>>>>>>> +++ b/hw/acpi/pcihp.c > >>>>>>>> @@ -116,6 +116,12 @@ static void acpi_set_pci_info(void) > >>>>>>>> bsel_is_set = true; > >>>>>>>> > >>>>>>>> if (!host) { > >>>>>>>> + /* > >>>>>>>> + * This function can be eventually called from > >>>>>>>> + * qemu_devices_reset() -> acpi_pcihp_reset() even > >>>>>>>> + * for architectures other than i386. Hence, we need > >>>>>>>> + * to ignore null values for host here. > >>>>>>>> + */ > >>>>>>>> return; > >>>>>>>> } > >>>>>>> > >>>>>>> I suspect it's a MIPS target that call this code unnecessarily. > >>>>>>> It would be better to get rid of this condition altogether. > >>>>>>> Frr that I can suggest to make acpi_pcihp_reset() stub and > >>>>>>> replace pcihp.c with stub (perhaps use acpi-x86-stub.c) when building > >>>>>>> for MIPS. > >>>>>>> > >>>>>>> then a bunch of asserts/ifs won't be necessary, > >>>>>>> just one in acpi_get_i386_pci_host() will be sufficient. > >>>>>>> > >>>>>> > >>>>>> OK this is a good idea. > >>>>>> I can see that mips-softmmu-config-devices.h has > >>>>>> CONFIG_ACPI_X86 turned on for mips. This does not seem right. > >>>>>> > >>>>>> The issue here is: > >>>>>> > >>>>>> $ grep -R CONFIG_ACPI_X86 * > >>>>>> devices/mips-softmmu/common.mak:CONFIG_ACPI_X86=y > >>>>>> > >>>>>> So after > >>>>>> > >>>>>> -CONFIG_ACPI_X86=y > >>>>>> -CONFIG_PIIX4=y > >>>>>> > >>>>>> (the second one is needed because after removing first one we get: > >>>>>> > >>>>>> /usr/bin/ld: libcommon.fa.p/hw_isa_piix4.c.o: in function `piix4_create': > >>>>>> /home/anisinha/workspace/qemu/build/../hw/isa/piix4.c:269: undefined > >>>>>> reference to `piix4_pm_init' > >>>>>> > >>>>>> This is because in hw/acpi/meson.build, piix4.c is conditional on > >>>>>> CONFIG_ACPI_X86. ) > >>>>>> > >>>>>> /usr/bin/ld: libqemu-mips-softmmu.fa.p/hw_mips_gt64xxx_pci.c.o: in > >>>>>> function `gt64120_pci_set_irq': > >>>>>> /home/anisinha/workspace/qemu/build/../hw/mips/gt64xxx_pci.c:1020: > >>>>>> undefined reference to `piix4_dev' > >>>>>> /usr/bin/ld: libqemu-mips-softmmu.fa.p/hw_mips_malta.c.o: in function > >>>>>> `mips_malta_init': > >>>>>> /home/anisinha/workspace/qemu/build/../hw/mips/malta.c:1404: undefined > >>>>>> reference to `piix4_create' > >>>>>> > >>>>>> So should mips be doing piix stuff anyway? Is Piix4 etc not x86 specific? > > > > PIIX, PIIX3 and PIIX4 are generic chipsets, not X86-specific. > > > > QEMU's PIIX3 is a Frankenstein to support virtualization to a chipset > > not designed for it. > > If you look at it, the X86 machine use a PIIX3 but the PIIX3 doesn't > > even provide an ACPI function. It appeared in the PIIX4. The kludge is > > to instanciate the PIIX4.acpi from the PIIX3 and X86 ppl are happy with > > it, but it makes it ugly for the other architectures. > > > >>>>> Apparently this is by design: > >>>>> https://qemu.readthedocs.io/en/stable/system/target-mips.html > > > > What do you mean "by design"? The Malta uses a PIIX4 chipset for its > > southbridge indeed. > > > >>>>> which means mips malta will continue to use the x86 specific functions > >>>>> like acpi_pcihp_reset(). Creating a stub for this with acpi-x86-stub.c > >>>>> will result in a double symbol definition because CONFIG_PC is off for > >>>>> mips. > >>>>> > >>>> > >>>> Also to be noted that there is a stub for acpi_get_i386_pci_host() which > >>>> simply returns NULL. This activates when CONFIG_PC is disabled. It is this > >>>> stub that gets called for mips and hence the check for non-null host is > >>>> needed in acpi_set_pci_info() function. > >>> that were half measures to deal around code that shouldn't be called, > >>> now with pcihp being used by both pc and q35 we don't have reason to > >>> keep around null checks modulo mips calling code that shouldn't be > >>> called there to begin with. > >> > >> So malta mips does not need ACPI hotplug? In that case, maybe we should > >> not make pcihp.c dependent on CONFIG_ACPI_X86. Ideas welcome. > > > > Linux on Malta does use the ACPI features from the PIIX4. > > > > Please dig in the archives, Igor / myself already argued enough about > > this topic 2 years ago. The consensus was "yes, it is badly implemented, > > but it works and we don't have time to get it cleaner, pc machine is > > way more used than the malta one, so let not break the pc machines." > > > > See: > > https://www.mail-archive.com/qemu-devel@nongnu.org/msg613194.html > > https://www.mail-archive.com/qemu-devel@nongnu.org/msg690435.html > > https://www.mail-archive.com/qemu-devel@nongnu.org/msg725504.html > > Also: > https://gitlab.com/qemu-project/qemu/-/issues/193 > https://gitlab.com/qemu-project/qemu/-/issues/221 Thanks Phil for the contexts. I will go through them. For now, should we simply go with my v2 then?
On Fri, 6 Aug 2021, Philippe Mathieu-Daudé wrote: > On 8/6/21 12:52 PM, Ani Sinha wrote: > > On Fri, 6 Aug 2021, Igor Mammedov wrote: > >> On Thu, 5 Aug 2021 19:42:35 +0530 (IST) > >> Ani Sinha <ani@anisinha.ca> wrote: > >>> On Thu, 5 Aug 2021, Ani Sinha wrote: > >>>> On Thu, 5 Aug 2021, Ani Sinha wrote: > >>>>> On Thu, 5 Aug 2021, Igor Mammedov wrote: > >>>>>> On Mon, 26 Jul 2021 22:27:43 +0530 > >>>>>> Ani Sinha <ani@anisinha.ca> wrote: > >>>>>> > >>>>>>> All existing code using acpi_get_i386_pci_host() checks for a non-null > >>>>>>> return value from this function call. Instead of returning early when the value > >>>>>>> returned is NULL, assert instead. Since there are only two possible host buses > >>>>>>> for i386 - q35 and i440fx, a null value return from the function does not make > >>>>>>> sense in most cases and is likely an error situation. > >>>>>>> > >>>>>>> Fixes: c0e427d6eb5fef ("hw/acpi/ich9: Enable ACPI PCI hot-plug") > >>>>>>> > >>>>>>> Signed-off-by: Ani Sinha <ani@anisinha.ca> > >>>>>>> --- > >>>>>>> hw/acpi/pcihp.c | 8 ++++++++ > >>>>>>> hw/i386/acpi-build.c | 15 ++++++--------- > >>>>>>> 2 files changed, 14 insertions(+), 9 deletions(-) > >>>>>>> > >>>>>>> changelog: > >>>>>>> v1: initial patch > >>>>>>> v2: removed comment addition - that can be sent as a separate patch. > >>>>>>> v3: added assertion for null host values for all cases except one. > >>>>>>> > >>>>>>> diff --git a/hw/acpi/pcihp.c b/hw/acpi/pcihp.c > >>>>>>> index f4d706e47d..054ee8cbc5 100644 > >>>>>>> --- a/hw/acpi/pcihp.c > >>>>>>> +++ b/hw/acpi/pcihp.c > >>>>>>> @@ -116,6 +116,12 @@ static void acpi_set_pci_info(void) > >>>>>>> bsel_is_set = true; > >>>>>>> > >>>>>>> if (!host) { > >>>>>>> + /* > >>>>>>> + * This function can be eventually called from > >>>>>>> + * qemu_devices_reset() -> acpi_pcihp_reset() even > >>>>>>> + * for architectures other than i386. Hence, we need > >>>>>>> + * to ignore null values for host here. > >>>>>>> + */ > >>>>>>> return; > >>>>>>> } > >>>>>> > >>>>>> I suspect it's a MIPS target that call this code unnecessarily. > >>>>>> It would be better to get rid of this condition altogether. > >>>>>> Frr that I can suggest to make acpi_pcihp_reset() stub and > >>>>>> replace pcihp.c with stub (perhaps use acpi-x86-stub.c) when building > >>>>>> for MIPS. > >>>>>> > >>>>>> then a bunch of asserts/ifs won't be necessary, > >>>>>> just one in acpi_get_i386_pci_host() will be sufficient. > >>>>>> > >>>>> > >>>>> OK this is a good idea. > >>>>> I can see that mips-softmmu-config-devices.h has > >>>>> CONFIG_ACPI_X86 turned on for mips. This does not seem right. > >>>>> > >>>>> The issue here is: > >>>>> > >>>>> $ grep -R CONFIG_ACPI_X86 * > >>>>> devices/mips-softmmu/common.mak:CONFIG_ACPI_X86=y > >>>>> > >>>>> So after > >>>>> > >>>>> -CONFIG_ACPI_X86=y > >>>>> -CONFIG_PIIX4=y > >>>>> > >>>>> (the second one is needed because after removing first one we get: > >>>>> > >>>>> /usr/bin/ld: libcommon.fa.p/hw_isa_piix4.c.o: in function `piix4_create': > >>>>> /home/anisinha/workspace/qemu/build/../hw/isa/piix4.c:269: undefined > >>>>> reference to `piix4_pm_init' > >>>>> > >>>>> This is because in hw/acpi/meson.build, piix4.c is conditional on > >>>>> CONFIG_ACPI_X86. ) > >>>>> > >>>>> /usr/bin/ld: libqemu-mips-softmmu.fa.p/hw_mips_gt64xxx_pci.c.o: in > >>>>> function `gt64120_pci_set_irq': > >>>>> /home/anisinha/workspace/qemu/build/../hw/mips/gt64xxx_pci.c:1020: > >>>>> undefined reference to `piix4_dev' > >>>>> /usr/bin/ld: libqemu-mips-softmmu.fa.p/hw_mips_malta.c.o: in function > >>>>> `mips_malta_init': > >>>>> /home/anisinha/workspace/qemu/build/../hw/mips/malta.c:1404: undefined > >>>>> reference to `piix4_create' > >>>>> > >>>>> So should mips be doing piix stuff anyway? Is Piix4 etc not x86 specific? > > PIIX, PIIX3 and PIIX4 are generic chipsets, not X86-specific. > > QEMU's PIIX3 is a Frankenstein to support virtualization to a chipset > not designed for it. > If you look at it, the X86 machine use a PIIX3 but the PIIX3 doesn't > even provide an ACPI function. It appeared in the PIIX4. The kludge is > to instanciate the PIIX4.acpi from the PIIX3 and X86 ppl are happy with > it, but it makes it ugly for the other architectures. > > >>>> Apparently this is by design: > >>>> https://qemu.readthedocs.io/en/stable/system/target-mips.html > > What do you mean "by design"? The Malta uses a PIIX4 chipset for its > southbridge indeed. I meant it was intentional and not by accident. > > >>>> which means mips malta will continue to use the x86 specific functions > >>>> like acpi_pcihp_reset(). Creating a stub for this with acpi-x86-stub.c > >>>> will result in a double symbol definition because CONFIG_PC is off for > >>>> mips. > >>>> > >>> > >>> Also to be noted that there is a stub for acpi_get_i386_pci_host() which > >>> simply returns NULL. This activates when CONFIG_PC is disabled. It is this > >>> stub that gets called for mips and hence the check for non-null host is > >>> needed in acpi_set_pci_info() function. > >> that were half measures to deal around code that shouldn't be called, > >> now with pcihp being used by both pc and q35 we don't have reason to > >> keep around null checks modulo mips calling code that shouldn't be > >> called there to begin with. > > > > So malta mips does not need ACPI hotplug? In that case, maybe we should > > not make pcihp.c dependent on CONFIG_ACPI_X86. Ideas welcome. > > Linux on Malta does use the ACPI features from the PIIX4. > > Please dig in the archives, Igor / myself already argued enough about > this topic 2 years ago. The consensus was "yes, it is badly implemented, > but it works and we don't have time to get it cleaner, pc machine is > way more used than the malta one, so let not break the pc machines." > > See: > https://www.mail-archive.com/qemu-devel@nongnu.org/msg613194.html > https://www.mail-archive.com/qemu-devel@nongnu.org/msg690435.html > https://www.mail-archive.com/qemu-devel@nongnu.org/msg725504.html Ok I see what you were trying to do. I wanted to stub out the cpu and memory hotplug bits for non x86 from piix4_acpi_system_hot_add_init(). Howwver, sadly, arm uses memory hotplug for its GED device: cff51ac978c4fa0b3d0de0fd ("hw/arm/virt: Enable device memory cold/hot plug with ACPI boot") This makes things messy and complicated. Anyways, I am trying something and will send out a patch if I am successful.
diff --git a/hw/acpi/pcihp.c b/hw/acpi/pcihp.c index f4d706e47d..054ee8cbc5 100644 --- a/hw/acpi/pcihp.c +++ b/hw/acpi/pcihp.c @@ -116,6 +116,12 @@ static void acpi_set_pci_info(void) bsel_is_set = true; if (!host) { + /* + * This function can be eventually called from + * qemu_devices_reset() -> acpi_pcihp_reset() even + * for architectures other than i386. Hence, we need + * to ignore null values for host here. + */ return; } @@ -136,6 +142,8 @@ static void acpi_pcihp_disable_root_bus(void) return; } + assert(host); + bus = PCI_HOST_BRIDGE(host)->bus; if (bus) { /* setting the hotplug handler to NULL makes the bus non-hotpluggable */ diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c index 17836149fe..83fb1d55c0 100644 --- a/hw/i386/acpi-build.c +++ b/hw/i386/acpi-build.c @@ -321,9 +321,7 @@ static void acpi_get_pci_holes(Range *hole, Range *hole64) pci_host = acpi_get_i386_pci_host(); - if (!pci_host) { - return; - } + assert(pci_host); range_set_bounds1(hole, object_property_get_uint(pci_host, @@ -1769,9 +1767,9 @@ build_dsdt(GArray *table_data, BIOSLinker *linker, pci_host = acpi_get_i386_pci_host(); - if (pci_host) { - bus = PCI_HOST_BRIDGE(pci_host)->bus; - } + assert(pci_host); + + bus = PCI_HOST_BRIDGE(pci_host)->bus; if (bus) { Aml *scope = aml_scope("PCI0"); @@ -2389,9 +2387,8 @@ static bool acpi_get_mcfg(AcpiMcfgInfo *mcfg) QObject *o; pci_host = acpi_get_i386_pci_host(); - if (!pci_host) { - return false; - } + + assert(pci_host); o = object_property_get_qobject(pci_host, PCIE_HOST_MCFG_BASE, NULL); if (!o) {
All existing code using acpi_get_i386_pci_host() checks for a non-null return value from this function call. Instead of returning early when the value returned is NULL, assert instead. Since there are only two possible host buses for i386 - q35 and i440fx, a null value return from the function does not make sense in most cases and is likely an error situation. Fixes: c0e427d6eb5fef ("hw/acpi/ich9: Enable ACPI PCI hot-plug") Signed-off-by: Ani Sinha <ani@anisinha.ca> --- hw/acpi/pcihp.c | 8 ++++++++ hw/i386/acpi-build.c | 15 ++++++--------- 2 files changed, 14 insertions(+), 9 deletions(-) changelog: v1: initial patch v2: removed comment addition - that can be sent as a separate patch. v3: added assertion for null host values for all cases except one.